Neb. Rev. Stat. § 23-139: Special tax fund; reversion to general fund.

Whenever a tax is levied for the payment of a specific debt, the amount of such tax collected shall be kept as a separate fund in the county treasury, and expended only in the liquidation of such indebtedness; Provided, any surplus remaining in the treasury after full payment of such indebtedness shall be transferred to the general fund of the county.